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Antigens

Antigens. Ali Al Khader, MD Faculty of Medicine Al-Balqa’ Applied University Email: ali.alkhader@bau.edu.jo. = S pecific structures in microbes/foreign materials that the body responds to by adaptive responses *3 receptors for antigens : 1- On B cells…or secreted from B cells

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Antigens

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  1. Antigens Ali Al Khader, MD Faculty of Medicine Al-Balqa’ Applied University Email: ali.alkhader@bau.edu.jo

  2. = Specific structures in microbes/foreign materials that the body responds to by adaptive responses *3 receptors for antigens: 1-On B cells…or secreted from B cells *Antibody (soluble receptor for antigen) 2-On T cells 3-Major histocompatibility complex (MHC)…= human leukocyte antigen (HLA)…encoded by a cluster of genes Function: presentation of antigenic peptides to T cells

  3. More about receptors for antigens… • B cell: binds the antigen directly without the need of a MHC molecule …but T cell bind both: antigen + MHC bound to the antigen *in this case the Ag is cell-associated (virus…etc)

  4. “Epitope” is the recognized part of “antigen” • Epitope is the real small part that is identified by the receptor • For example, a protein is an antigen but a small amino acid sequence of the protein is the real part that is specific for the receptor …single molecule may have multiple epitopes • The two terms are usually used interchangeably

  5. 2 types of epitope Antibodies can recognize both types T cells recognize only linear type (bound to MHC) Immunology for medical students 2ndedition..modified

  6. Antigen VS immunogen • Antigen may bind to the receptor but may not induce antibody production (ineffective binding) • Immunogen is the effective antigen that elicit antibody production • To be effective, the molecule needs to be larger and more complex and fit more to the receptor • Proteins are more immunogenic than carbohydrates and lipids • Enzymatically-cleavable proteins are more immunogenic than non-cleavable ones

  7. Haptens • They are simple molecules that are non-immunogenic…but if they are coupled to a larger molecule (an immunogen) which is called “carrier”, they bind effectively to the receptor, and now the response is directed toward both the hapten and the carrier epitope • They are usually non-biological

  8. End of appetizers… Relax & recharge for the next week

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